Abstract: Like humans, social insects are highly responsive to their social environment and therefore are great potential systems to study the effects of social interactions on individual behavior and physiology. Here I propose to develop and use a novel genetic model system, the ant Cerapachys biroi, to study the following main questions. 1. Which basic molecular components are required for individuals to function as a society? 2. How are these components derived from the genetic architecture of solitary ancestors? 3. How does evolutionary change at the individual level give rise to novel forms of social organization? Cerapachys biroi is perfectl suited as a model system because it uniquely combines fascinating social behavior with unparalleled experimental accessibility. Workers reproduce parthenogenetically, which means that the individual allelic background and the genetic composition of experimental colonies can be perfectly controlled and replicated. The species also has a peculiar form of social organization. While colonies of other social insects perform different tasks simultaneously, colonies of C. biroi undergo highly stereotyped behavioral and reproductive cycles. These colony-level cycles emerge from the workers' synchronized response to pheromone and tactile stimuli from the brood. The social environment is therefore precisely defined by the different brood developmental stages present in the colony. This form of social organization allows me to precisely control, replicate, and experimentally manipulate the social environment. As a foundation for future work, my lab is currently sequencing the genome and transcriptome of C. biroi and developing automated techniques to quantify individual and colony-level behavior. As a NIH New Innovator, I first plan to quantify cyclic behavior and associated changes in global gene expression using RNA-Seq experiments. This will identify candidate molecular pathways that are responsive to changes in the social environment. As a second step, my group will characterize the function and regulation of particular candidate genes and pathways by using a combination of targeted approaches (RT-qPCR, immunostaining, pharmacological and genetic manipulations, etc.). In comparison to solitary model organisms, this will shed light on how the molecular architecture of social species builds on that of their solitary ancestors, and which components have evolved entirely de novo. Finally, by comparing C. biroi to other social insects, we will study how the derived cyclic social organization emerges from evolutionary change at the individual level. Public Health Relevance: Similar to humans, social insects are highly responsive to the social environment and therefore are great systems to study the effects of social interactions on individual behavior and physiology. Using a novel ant model system, I will investigate the fundamental molecular and genetic mechanisms that underlie social life. This work will potentially also have important implications for our basic understanding of the human social mind.